German to English Law/Patents Law: Contract(s) Call for competition

This comes from a call for competition for IT services. This section outlines the contractual terms between the contracting authority and the contractor. The preceding sentence states that the contractor is liable for the proper completion of the overall project, even in cases where subcontractors are involved and then comes this:

"Etwaiges fehlendes Auswahlverschulden kann nicht geltend gemacht werden."

Auswahlverschulden as I understand it is negligence in the selection of the subcontractor, but what I don't understand is how someone could or could not claim a "lack of negligence" in the selection.

Thanks in advance for your assistance